X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 20 Jun 2011 08:00:14 -0400 Message-ID: X-Original-Return-Path: Received: from elasmtp-dupuy.atl.sa.earthlink.net ([209.86.89.62] verified) by logan.com (CommuniGate Pro SMTP 5.4.0) with ESMTP id 5025641 for lml@lancaironline.net; Mon, 20 Jun 2011 00:04:48 -0400 Received-SPF: none receiver=logan.com; client-ip=209.86.89.62; envelope-from=colyncase@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=EHBK2EVXkHtqV6BC5tuEBDo/HLshFMWgrUsv2+VlMF+45l03I6xLpvnibaQ8PFqD; h=Received:From:Mime-Version:Content-Type:Subject:Date:In-Reply-To:To:References:Message-Id:X-Mailer:X-ELNK-Trace:X-Originating-IP; Received: from [66.201.52.88] (helo=[10.71.0.104]) by elasmtp-dupuy.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1QYVie-0006Ah-MW for lml@lancaironline.net; Mon, 20 Jun 2011 00:04:13 -0400 From: Colyn Case Mime-Version: 1.0 (Apple Message framework v1082) Content-Type: multipart/alternative; boundary=Apple-Mail-673--477030165 Subject: Re: [LML] Re: And how about a full feathering prop? X-Original-Date: Sun, 19 Jun 2011 21:04:11 -0700 In-Reply-To: X-Original-To: "Lancair Mailing List" References: X-Original-Message-Id: <8B74E3C8-6D0D-4530-9900-FE3C5FDFC139@earthlink.net> X-Mailer: Apple Mail (2.1082) X-ELNK-Trace: 63d5d3452847f8b1d6dd28457998182d7e972de0d01da9401f1cd1701582892e9728bbc7e0ecdcfa350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 66.201.52.88 --Apple-Mail-673--477030165 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 Yes! that's the one, thanks for reposting. Thanks, Dan for the reminder about the counterweighted prop. So I guess there are actually 3 options? 1) full feathering: always goes to feather with loss of oil pressure 2) counterweighted: ?goes to almost feather with power loss (or is it = pressure loss) 3) normal constant speed: always goes to fine with oil pressure loss. So are the scenarios like this? I show in red any situation that is = undesirable. I think the most likely situation is power loss only followed by power = and pressure loss only. situation Full feathering = counterweighted constant speed pressure loss only feathered ? = fine power loss only pilot control pilot control = pilot control power and pressure loss feathered feathered = fine On Jun 19, 2011, at 4:56 PM, Sky2high@aol.com wrote: > Colyn, > =20 > Maybe you are referring to the included chart from "Aerodynamics for = Naval Aviators". The Hartzell prop for the 320 engine has a pitch range = of 12 to 40 degrees. If the engine has not seized (stationary prop), = pulling back to coarse pitch results in almost the same drag reduction = as a feathered prop. Slick Lancairs are affected greatly by such drag = as there are no struts, rivets or fat wings to moderate the effect. > =20 > In my 320, zero thrust, cruise pitch resulted in a 1500 fpm descent at = best glide (about 107 KIAS via AOA) and pulling back to coarse pitch the = descent rate decreased to about 400-500 fpm. It was an eye opener. > =20 > > =20 > Grayhawk > =20 > In a message dated 6/19/2011 10:31:36 A.M. Central Daylight Time, = colyncase@earthlink.net writes: > Those are very interesting numbers. > I think Scotty's got a chart that shows that the advantage of a full = feathering prop over constant speed is pretty marginal. >=20 > After I wrote my last post I realized that the 120 knots/600 fpm = number I had in my head was from a IV-PT which has less drag in the > nose than a IVP. Keeping that in mind, Bob's numbers are quite = impressive. >=20 > Bob points out that the prop is a nice adjustable speed brake when = windmilling. > I have not tried it but I suppose a fully featherable prop could do = the same thing IF you don't just yank it all the way back all at once. > Once you lose oil pressure you can't do anything with the fully = featherable prop unless you get one with an unfeathering accumulator (I = don't know of an approved one for the IVP - maybe someone else does). > Keeping the prop windmilling will keep you in oil pressure if you = don't have an oil leak. >=20 > Colyn >=20 >=20 > On Jun 18, 2011, at 5:32 PM, Robert R Pastusek wrote: >=20 >> Ronald wrote: >> =20 >> For what I have gathered so far the lancair 4p has a glide ratio = similar like a piano LOL In other words if the engine quits then open = the door, throw out your keys because there is where you land LOL >> =20 >> Well, this might not be true, or is it?=20 >> =20 >> So how about the full feathering prop ? Does anyone have experience = with the before and after installation? How much they cost and data? >> =20 >> And I needed to respond to this=85 >> =20 >> My IV-P has a glide ratio (at 120 KIAS) of between 5:1 and 20:1, = depending on configuration. The difference is truly = amazing/impressive/sobering=85 depending on your situation and mind set. = With the gear and flaps down and the RPM at max (prop all the way in), = the glide ratio approximates that of a brick=85not really, but you=92re = coming down so fast relative to forward progress that it=92s difficult = to plan and execute a planned touchdown (at least for me). With the gear = and flaps up, AND THE PROP CONTROL ALL THE WAY OUT, my glide ratio at = gross weight is approximately 18:1, increasing to a bit better than 20:1 = at 800# under gross. At this glide ratio, the performance and =93sight = picture=94 approximates that of some gliders. It=92s easy to plan and = execute an approach and landing to a pre-planned spot=85ideally a = runway. I have practiced this many times from various = altitudes/distances from the airport to a full stop on the runway, using = the gear to increase my descent rate, and then the flaps and/or the prop = control to adjust the touchdown point. Using the prop control is ideal = because the drag effect/descent rate increase almost immediately = reversible by pushing it back in. Not so with the flaps. One feature of = my Chelton EFIS is a wind-adjusted glide range predictor. I have tested = this many times starting at altitudes up to 17,500=92 and (set at 18:1) = gives me a very accurate and immediate sight picture of airfields within = glide range. If it=92s within the green circle, I can turn toward an = airfield and execute a safe landing there. My MT 4-blade is not full = feathering, but allows the engine to run at approximately 700 RPM when = at idle and the RPM set to min. I believe this is pretty close to 0 = thrust, as the engine idles at approximately 600 RPM on the ground.=20 >> =20 >> So, in summary, the throw out the keys and follow them down scenario = can be executed if you really want to go down, but a planned glide at = 120 KIAS (very close to best glide for my airplane) in clean = configuration yields approximately the performance of a 2-place sail = plane=97and you have the ability to transition easily between these = limits as needed. Try it; you=92ll be impressed. >> =20 >> Bob >> =20 >> PS: I considered and rejected a full feathering prop for what I have. = Wouldn=92t trade for any amount of money=85 >=20 > =3D > -- > For archives and unsub = http://mail.lancaironline.net:81/lists/lml/List.html --Apple-Mail-673--477030165 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=windows-1252 Yes! = that's the one, thanks for reposting.

Thanks, Dan for = the reminder about the counterweighted prop.

So = I guess there are actually 3 options?
1) full feathering: = always goes to feather with loss of oil pressure
2) = counterweighted: ?goes to almost feather with power loss (or is it = pressure loss)
3) normal constant speed: always goes to fine = with oil pressure loss.

So are the scenarios = like this?   I show in red any situation that is = undesirable.
I think the most likely situation is power loss = only followed by power and pressure loss = only.

 situation             =                =  Full feathering =            counterweighted     =      constant speed

pressure loss only   =            feathered             =      ?               =          fine

power loss only   =               pilot control     =          pilot control       =      pilot control

power and pressure loss =         feathered         =          feathered         =        fine


On Jun 19, = 2011, at 4:56 PM, Sky2high@aol.com= wrote:

Colyn,
 
Maybe you are referring to the included chart from = "Aerodynamics=20 for Naval Aviators".  The Hartzell prop for the 320 engine has a = pitch=20 range of 12 to 40 degrees.  If the engine has not seized = (stationary prop),=20 pulling back to coarse pitch results in almost the same drag reduction = as a=20 feathered prop.  Slick Lancairs are affected greatly by such drag = as there=20 are no struts, rivets or fat wings to moderate the effect.
 
In my 320, zero thrust, cruise pitch resulted in a 1500 fpm = descent at=20 best glide (about 107 KIAS via AOA) and pulling back to coarse pitch the = descent=20 rate decreased to about 400-500 fpm.  It was an eye opener.
 
<Prop%20Drag.jpg>
 
Grayhawk
 
In a message dated 6/19/2011 10:31:36 A.M. Central Daylight Time,=20= colyncase@earthlink.net = writes:
Those=20 are very interesting numbers.=20
I think Scotty's got a chart that shows that the advantage of a = full=20 feathering prop over constant speed is pretty marginal.

After I wrote my last post I realized that the 120 knots/600 fpm = number I=20 had in my head was from a IV-PT which has less drag in the
nose than a IVP.  Keeping that in mind, Bob's numbers are = quite=20 impressive.

Bob points out that the prop is a nice adjustable speed brake = when=20 windmilling.
I have not tried it but I suppose a fully featherable prop could = do the=20 same thing IF you don't just yank it all the way back all at = once.
Once you lose oil pressure you can't do anything with the fully=20= featherable prop unless you get one with an unfeathering accumulator = (I don't=20 know of an approved one for the IVP - maybe someone else does).
Keeping the prop windmilling will keep you in oil pressure if you = don't=20 have an oil leak.

Colyn


On Jun 18, 2011, at 5:32 PM, Robert R Pastusek wrote:

Ronald=20 wrote:
 
For=20 what I have gathered so far the lancair 4p has a glide ratio similar = like a=20 piano LOL In other words if the engine quits then open the door, = throw out=20 your keys because there is where you land = LOL
 
Well,=20 this might not be true, or is = it? 
 
So=20 how about the full feathering prop ? Does anyone have experience = with the=20 before and after installation?  How much they cost and=20 data?
 
And=20 I needed to respond to this=85
 
My=20 IV-P has a glide ratio (at 120 KIAS) of between 5:1 and 20:1, = depending on=20 configuration. The difference is truly amazing/impressive/sobering=85=20= depending on your situation and mind set. With the gear and flaps = down and=20 the RPM at max (prop all the way in), the glide ratio approximates = that of a=20 brick=85not really, but you=92re coming down so fast relative to = forward=20 progress that it=92s difficult to plan and execute a planned = touchdown (at=20 least for me). With the gear and flaps up, AND THE PROP CONTROL ALL = THE WAY=20 OUT, my glide ratio at gross weight is approximately 18:1, = increasing to a=20 bit better than 20:1 at 800# under gross. At this glide ratio, the=20= performance and =93sight picture=94 approximates that of some = gliders. It=92s easy=20 to plan and execute an approach and landing to a pre-planned = spot=85ideally a=20 runway. I have practiced this many times from various = altitudes/distances=20 from the airport to a full stop on the runway, using the gear to = increase my=20 descent rate, and then the flaps and/or the prop control to adjust = the=20 touchdown point. Using the prop control is ideal because the drag=20 effect/descent rate increase almost immediately reversible by = pushing it=20 back in. Not so with the flaps.  One feature of my = Chelton=20 EFIS is a wind-adjusted glide range predictor. I have tested this = many times=20 starting at altitudes up to 17,500=92 and  (set at = 18:1)=20 gives me a very accurate and immediate sight picture of airfields = within=20 glide range. If it=92s within the green circle, I can turn toward an = airfield=20 and execute a safe landing there. My MT 4-blade is not full = feathering, but=20 allows the engine to run at approximately 700 RPM when at idle and = the RPM=20 set to min. I believe this is pretty close to 0 thrust, as the = engine idles=20 at approximately 600 RPM on the ground. 
 
So,=20 in summary, the throw out the keys and follow them down scenario can = be=20 executed if you really want to go down, but a planned glide at 120 = KIAS=20 (very close to best glide for my airplane) in clean configuration = yields=20 approximately the performance of a 2-place sail plane=97and you have = the=20 ability to transition easily between these limits as needed. Try it; = you=92ll=20 be  impressed.<= /span>
 
Bob
 
PS:=20 I considered and rejected a full feathering prop for what I have.=20 Wouldn=92t  trade for any amount = of=20 = money=85

=3D
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